Ventilator Waveform Analysis


Pressure Time

  1. Determine CPAP level
  2. Is patient triggering?
  3. Shape of pressure wave

Flow Time

  1. Flow pattern
  2. Is the patient gas trapping?
  3. If patient is triggering is it pressure supported, SIMV or VAC?
  4. If patient is triggering is it pressure support or pressure controlled?
  5. Is the patient synchronizing well with ventilator?


Pressure vs Time

  • type of ventilation
  • peak pressure
  • plateau pressure
  • PEEP
  • compliance calculation
  • patient triggering
  • adequacy of inspiratory flow
  • presence of auto-PEEP, presence of dynamic hyperinflation and occult PEEP
  • presence of circuit leak

Volume vs Time Graph

  • TV
  • type of flow pattern
  • inspiratory and expiratory time

Flow vs Time

  • wave form: square -> volume, decelerating -> pressure, sinusoidal
  • inspiratory time
  • expiratory time
  • auto PEEP

Pressure Volume Loops

  • compliance
  • lower inflection point
  • upper inflection point
  • PEEP level
  • peak inspiratory pressure
  • whether spontaneously breathing (effort required to trigger breath)
  • overdistension
  • leaks or airtrapping

Flow Volume Loops

  • peak inspiratory flow rate
  • peak expiratory flow rate
  • tidal volume
  • type of lung and airway pathology
  • leaks or air trapping
  • water or secretions in circuit

References and Links


FOAM and web resources

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.